The majority of human epithelial cancers is frequently characterized by a functional activation of the epidermal growth factor receptor (EGFR)-driven-pathways. Today, two classes of EGFR inhibitors are routinely used in the clinic: anti-EGFR monoclonal antibodies such as cetuximab and panitumumab and small-molecule inhibitors of the EGFR tyrosine kinase activity such as erlotinib and gefitinib. Anti-EGFR therapies have been approved in several countries for the treatment of metastatic nonsmall-cell lung cancer, colorectal cancer, squamous-cell carcinoma of the head and neck, and pancreatic cancer. This article summarizes the clinical evidence of the anticancer activity of anti-EGFR treatment, and considers the current, and controversial, clinical issues with respect to their optimal use in the treatment of patients with cancer. Mechanisms of resistance to anti-EGFR treatment are also briefly discussed.